Power supply device, power supply system and method for controlling the same

ABSTRACT

A power supply system may include a target device and an adapter. The target device may include an adapter connection switch that receives adapter recognition information to form a connection with the adapter, a voltage detection unit that receives an output voltage from an adapter, and a voltage-change-requesting unit that outputs a voltage to request a voltage change based on information on the output voltage from the adapter. The adapter may include a device information recognition unit that receives the voltage to request a voltage change, and an output-voltage-changing unit that changes the output voltage based on the voltage to request a voltage change.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/273,444 filed on May 8, 2014, which claims the benefit of KoreanPatent Application No. 10-2013-0131602 filed on Oct. 31, 2013, with theKorean Intellectual Property Office, the disclosures of which areincorporated herein by reference.

BACKGROUND

The present disclosure relates to a power supply system including ageneral-purpose power supply device.

Recently, portable electronic devices have tended to be operatedsystemically and wirelessly, to provide multimedia services, and to bedigitalized, “smart” and relatively complex. In particular, multimediaservices are increasingly attracting popular interest, and accordingly,multimedia services provided by small, portable devices have come toprominence.

Among portable electronic devices, as mobile devices such as smartphonesand tablet personal computers (PCs) are prominent as informationtechnology devices, new technology requirements for driving powersupplying devices such as adapters for charging batteries in such mobiledevices have also been increased.

Previously, only the standby power of driving power supply devices hasbeen specified. However, as many features, including touchscreens, havebeen added to mobile devices, it has become necessary to reduce theinfluence of such device elements on mobile devices while driving powersupply devices are charging such mobile devices.

As mobile devices are diversified in terms of the available typesthereof, it is necessary to supply power to different mobile deviceshaving different power specifications using a single power supplydevice. Accordingly, research into a power supply devices applicable todifferent mobile devices ongoing.

That is, different mobile devices have different rated voltages, andthus require dedicated power supply devices. For this reason, not tomention the cost burden, users have to carry as many power supplydevices as they do mobile devices.

As a solution to solve such problems, setting a common input voltage formobile devices at, 5 V, for example, may be contemplated. In such asolution, however, a laptop computer, for example, may require a highlevel of input power and thus consume a large amount of current, suchthat a separate heat dissipation device may be required to dissipateheat generated in the device.

In such a case, the volume of the power supply device is inevitablyincreased along with manufacturing costs thereof.

In the case that output voltage from the power supply device is set tobe 12 V, even though the current may be decreased, it may force devices(such as smartphones) that have low input voltage and employ small andcheap elements to employ elements having higher withstand voltage levelsto handle the increased input voltage. This results in an increase inmanufacturing costs, as elements having higher withstand voltages aregenerally more expensive than elements having lower withstand voltages.Therefore, it may be difficult to use a power supply device thatsupplies power having a a single voltage level to various devices.

Patent Documents 1 and 2 listed below relate to a unified power supplydevice. However, such a unified power supply device includes powersupply circuits for supplying various levels of voltage, so that thevolume of the device is increased and thus manufacturing costs areincreased.

Therefore, in order to overcome the above problems, a novel power supplydevice is required that can be used for various devices.

RELATED ART DOCUMENT

-   (Patent Document 1) Korean Patent Laid-Open Publication No.    2009-0031085-   (Patent Document 2) Korean Patent Laid-Open Publication No.    2007-0006969

SUMMARY

An aspect of the present disclosure may provide a general-purpose powersupply system that can be used for a variety of devices requiringdriving power having different voltage and current levels.

According to an aspect of the present disclosure, a power supply systemmay include: a target device and an adapter, the target device includingan adapter connection switch that receives adapter recognitioninformation to form a connection with the adapter, a voltage detectionunit that receives an output voltage from the adapter, and avoltage-change-requesting unit that outputs a signal to request avoltage change based on information on the output voltage from theadapter; and the adapter including a device information recognition unitthat receives the signal to request a voltage change, and anoutput-voltage-changing unit that changes the output voltage based onthe signal to request a voltage change.

The voltage-change-requesting unit in the target device may be connectedto the device information recognition unit in the adapter via a USB datacable.

The adapter may further include an adapter information output unit thatoutputs adapter information to the target device.

The target device may further include a control unit operably connectedto the adapter connection switch, the voltage detection unit and thechange-requesting unit.

The adapter may further include a control unit operably connected to thedevice information recognition unit and the output-voltage-changingunit.

The device information recognition unit may include voltage-dividingresistors to detect a level of a voltage in the USB data cable.

According to another aspect of the present disclosure, a power supplysystem may include a target device and an adapter, the target deviceincluding an adapter connection switch that receives adapter recognitioninformation to form a connection with the adapter, a voltage detectionunit that receives an output voltage from an adapter, and avoltage-change-requesting unit that outputs a voltage to request avoltage change based on information on the output voltage from theadapter; and the adapter including a device information recognition unitthat receives the voltage to request a voltage change, and anoutput-voltage-changing unit that changes the output voltage based onthe voltage to request a voltage change.

The voltage-change-requesting unit in the target device may be connectedto the device information recognition unit in the adapter via a USB datacable, and the device information recognition unit may includevoltage-dividing resistors to detect a level of a voltage in the USBdata cable.

According to another aspect of the present disclosure, a method forcontrolling a power supply system may include: determining whether adevice is connected at a first time point and at a second time point;determining a specification for supplying power based on whether thedevice is connected at the first time point and on whether the device isconnected at the second time point; and supplying power based on thespecification for supplying power.

The determining of the specification for supplying power may include:receiving the signal to request a voltage change to change thespecification for supplying power, if it is determined that the deviceis connected at the first time point and that the device is disconnectedat the second time point.

The determining of the specification for supplying power may include:maintaining the specification for supplying power, if it is determinedthat the device is connected at the first time point and that the deviceis connected at the second time point.

According to another aspect of the present disclosure, a power supplydevice may include: a USB data cable; a device information recognitionunit that includes voltage-dividing resistors and receives a signal torequest a voltage change from a target device via the USB data cable;and an output-voltage-changing unit that changes an output voltage basedon the signal to request a voltage change.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram of a power supply system according to an exemplaryembodiment of the present disclosure;

FIG. 2 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 3 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 4 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 5 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 6 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 7 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 8 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure;

FIG. 9 is a flowchart for illustrating a method for controlling a powersupply system according to an exemplary embodiment of the presentdisclosure; and

FIG. 10 is a circuit diagram of an adapter according to anotherexemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. The disclosure may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the disclosure to thoseskilled in the art. Throughout the drawings, the same or like referencenumerals will be used to designate the same or like elements.

FIG. 1 is a diagram of a power supply system according to an exemplaryembodiment of the present disclosure.

Referring to FIG. 1 , the power supply system may include an adapter100, and a target device 200.

The target device 200 may be an electronic device which receives powerfrom the adapter 100 to charge a battery therein.

The target device 200 may include an adapter connection switch 210, avoltage detection unit 230, a voltage-change-requesting unit 220, acontrol unit 240, and an analog-to-digital converter (ADC) 250.

The control unit 240 may be operably connected to the adapter connectionswitch 210, the voltage detection unit 230, thevoltage-change-requesting unit 220, and the ADC 250, so that it maycontrol the adapter connection switch 210, the voltage detection unit230, the voltage-change-requesting unit 220, and the ADC 250.

The adapter connection switch 210 may receive adapter recognitioninformation and may form a connection with an adapter. The adapterrecognition information may include information as to whether an adapteris connected to a target device.

That is, if an adapter is connected to a target device, the targetdevice recognizes that the device connected thereto is an adapter andthen may switch on the adapter connection switch. For example, thetarget device may recognize that the connected device is an adapterbased on information on a USB data cable.

The voltage detection unit 230 may receive an output voltage from anadapter. The voltage detection unit 230 may include voltage-dividingresistors R11 and R12. The voltage detection unit 230 may detect anoutput voltage Vo from an adapter divided by the voltage-dividingresistors R11 and R12.

In this manner, the target device may receive the output voltage fromthe adapter.

The control unit 240 may check whether the output voltage from anadapter is equal to the rated voltage of the target device. If theoutput voltage from the adapter is equal to the rated voltage of thetarget device, a pass switch Qp is turned on so that a battery may besupplied with power.

If the output voltage from the adapter is not equal to the rated voltageof the target device, the target device 200 may output a signal torequest a voltage change to the adapter 100.

The voltage-change-requesting unit 220 may output the signal to requesta voltage change based on the output voltage from the adapter. That is,the voltage-change-requesting unit 220 may output a voltage to request avoltage change based on the output voltage from the adapter.

The voltage-change-requesting unit 220 may include a resistor and aswitch Q11. The switch Q11 may be connected between ground and aconnection node between the adapter connection switch 210 and the ADC250. Depending on switching of the switch Q11, the level of the voltageoutput from the voltage-change-requesting unit may be changed.

The adapter 100 may be connected to the target device 200 via a USB datacable V_(DATA). Further, the voltage-change-requesting unit 220 in thedevice may be connected to a device information recognition unit 140 inthe adapter via the adapter connection switch 210 and the USB data cableV_(DATA).

The voltage-change-requesting unit 220 may output the signal to requesta voltage change and the voltage to request a voltage change via the USBdata cable V_(DATA).

As described above, in the power supply system according to theexemplary embodiment of the present disclosure, information can betransmitted between the adapter and the target device via the existingUSB data cable V_(DATA), without employing any additional signal cable.

The ADC 250 may receive a signal from the voltage detection unit 230 andthe adapter connection switch 210 and may transmit it to the controlunit.

The adapter 100 may include a power supply unit, an output unit 110, anoutput-voltage-changing unit 120, a control unit 130, the deviceinformation recognition unit 140, and a low-dropout regulator (LDO) 150.

The power supply unit may change input power into driving power having apredetermined voltage level so as to supply it.

The output unit 110 may change the voltage of the power from the powersupply unit. The power with changed voltage may be regulated via avoltage regulator SR, in which a reference voltage is set by resistorsR1 and R2, and then it is output.

The device information recognition unit 140 may receive a signal torequest a voltage change from the target device. Specifically, thedevice information recognition unit 140 may detect a change in the levelof the voltage output from the voltage-change-requesting unit in thetarget device. In other words, the device information recognition unit140 may detect a change in the voltage on the USB data cable V_(DATA).

The device information recognition unit 140 may include voltage-dividingresistors R5 and R6. The device information recognition unit 140 maydetect the voltage on the USB data cable which has been divided by thevoltage-dividing resistors R5 and R6.

The output-voltage-changing unit 120 may change the output voltage basedon the signal to request a voltage change.

The output-voltage-changing unit 120 may include resistors R4 and R5 anda switch Q1. The resistor R4 may be connected to the output unit 110 inparallel.

Depending on switching of the switch Q1, the level of the voltage outputfrom the adapter may be changed.

The control unit 130 may be operably connected to the device informationrecognition unit 140 and to the output-voltage-changing unit and maycontrol the device information recognition unit 140 and theoutput-voltage-changing unit.

FIG. 2 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The power supply system shown in FIG. 2 is identical to the system shownin FIG. 1 , except for the control unit 130. Other elements than thecontrol unit 130 have been described above and, therefore, will not bedescribed again.

Referring to FIG. 2 , the control unit 130 may replace the deviceinformation recognition unit 140 shown in FIG. 1 . According to thisexemplary embodiment, the resistors used in the device informationrecognition unit 140 are eliminated, and device information isrecognized by resistors in the control unit 130. Therefore, the numberof used resistors may be reduced.

FIG. 3 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The power supply system shown in FIG. 3 is identical to the system shownin FIG. 1 , except for the control unit 130. Other elements than thecontrol unit 130 have been described above and, therefore, will not bedescribed again.

The control unit 130 may include a plurality of comparators and a NANDlogic circuit. The control unit 130 may output different signals when itreceives a voltage within a predetermined range, i.e., V_(REF−) andV_(REF+) and when it receives a voltage out of the predetermined range,i.e., V_(REF−) and V_(REF+).

Accordingly, the control unit 130 may not operate theoutput-voltage-changing unit 120 while the target device is beingsupplied with a rated voltage. Further, the control unit 130 may operatethe output-voltage-changing unit 120 while the target device is notbeing supplied with a rated voltage.

FIG. 4 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The power supply system shown in FIG. 4 is identical to the system shownin FIG. 1 , except for the voltage-change-requesting unit 220. Otherelements than the voltage-change-requesting unit 220 have been describedabove and, therefore, will not be described again.

The voltage-change-requesting unit 220 may include a resistor and aswitch Q11. The switch Q11 may be connected between an output cable Voand a connection node between the adapter connection switch 210 and theADC 250. Depending on switching of the switch Q11, the level of thevoltage output from the voltage-change-requesting unit may be changed.

FIG. 5 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The power supply system shown in FIG. 5 is identical to the system shownin FIG. 4 , except for the control unit 130. Other elements than thecontrol unit 130 have been described above and, therefore, will not bedescribed again.

Referring to FIG. 5 , the control unit 130 may replace the deviceinformation recognition unit 140 shown in FIG. 4 . According to thisexemplary embodiment, the resistors used in the device informationrecognition unit 140 are eliminated, and device information isrecognized by resistors in the control unit 130. Therefore, the numberof used resistors may be reduced.

FIG. 6 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The configuration of the power supply system shown in FIG. 6 will beapparent to those skilled in the art based on the descriptions givenwith respect to the FIGS. 1, 2, 3 and 4 and, therefore, will not bedescribed.

FIG. 7 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The power supply system shown in FIG. 7 is identical to the system shownin FIG. 1 , except for an adapter information output unit 160. Otherelements than the adapter information output unit 160 have beendescribed above and, therefore, will not be described again.

The adapter information output unit 160 may output adapter informationto a target device. The adapter information may indicate that theadapter is a variable-output adapter.

When an adapter is connected to a target device, the adapter informationoutput unit 160 may output adapter information to the target device.

The adapter information output unit 160 may include a resistor and aswitch Q2. The switch Q2 and the resistor may be connected to each otherin series and may be connected to the device information recognitionunit 140 in parallel.

Depending on switching of the switch Q2, the level of the voltage on aUSB data cable V_(DATA) may be changed.

Accordingly, the adapter information output unit 160 may deliver theadapter information to the target device via the USB data cableV_(DATA).

As described above, in the power supply system according to theexemplary embodiment of the present disclosure, information can betransmitted between the adapter and the target device via the existingUSB data cable V_(DATA), without employing any additional signal cable.

FIG. 8 is a diagram of a power supply system according to anotherexemplary embodiment of the present disclosure.

The power supply system shown in FIG. 8 is identical to the system shownin FIG. 7 , except for the control unit 130. Other elements than thecontrol unit 130 have been described above and, therefore, will not bedescribed again.

Referring to FIG. 8 , the control unit 130 may replace the deviceinformation recognition unit 140 shown in FIG. 7 . According to thisexemplary embodiment, the resistors used in the device informationrecognition unit 140 are eliminated, and device information isrecognized by resistors in the control unit 130. Therefore, the numberof used resistors may be reduced.

In this regard, the control unit 130 shown in FIGS. 1, 2, 4, 5, 7 and 8may be a controller in the adapter to transmit/receive signals and tochange an output voltage.

Further, the control unit 240 shown in FIGS. 1, 2, 4, 5, 7 and 8 may bean IC to implement the inherent function of the device or may be aseparate IC to perform voltage detection, voltage-change request or thelike, as described above.

The control unit 130 shown in FIGS. 3 and 6 may be implemented in ananalog manner and may diversify output voltage by adding circuits suchas a comparator, a logic gate, a flip-flop and the like if more voltagesare required by the device.

FIG. 10 is a circuit diagram of an adapter according to anotherexemplary embodiment of the present disclosure.

The adapter shown in FIG. 10 is identical to the adapter shown in FIG. 1, except for a disconnection-detecting unit 170. Other elements than thedisconnection-detecting unit 170 have been described above and,therefore, will not be described again.

The disconnection-detecting unit 170 may include a diode D_(DIS),resistors and a capacitor.

The level of the average input voltage of the diode D_(DIS) may bedifferent depending on the state of a target device. Depending on thestate of the device, the duty cycle of and frequency of a DC/DCconverter are changed, and accordingly the average input voltage of thediode D_(DIS) may be changed.

After the average input voltage is rectified by the diode D_(DIS), it isfiltered by the capacitor having small capacitance, and then a DC valuereflecting the state of a load may be detected. By using this value,disconnection of the device can be detected.

FIG. 9 is a flowchart for illustrating a method for controlling a powersupply system according to an exemplary embodiment of the presentdisclosure.

Referring to FIG. 10 , the adapter may check whether the device isdisconnected therefrom (S10). In doing so, the disconnection-detectingunit 170 shown in FIG. 9 may be used.

If it the adapter is disconnected from the device, the adapter mayoutput base output power (S20).

If the adapter is connected to the device, the adapter may check whetherthe adapter was disconnected from the device at a previous time point(S30).

That is, according to the method for controlling a power supply systemaccording to the exemplary embodiment of the present disclosure, it maybe determined whether the device is connected to the adapter at firstand second time points. The second time point is earlier than the firsttime point.

If the adapter is connected to the device at the first time point and atthe second time point, the adapter does not change its output voltage.

In the related art, while an adapter supplies power to a device afterthey are connected to each other and mutually check recognition signals,the recognition signals may be distorted due to a change in the state ofthe device or introduction of noise. When this happens, the adapter maysupply power to the device based on the erroneously recognized signal.At this time, an error occurs in the device and the device may bedamaged, unless a separate protection circuit is operated in the device.

In the method for controlling a power supply system according to theexemplary embodiment of the present disclosure, however, it isdetermined whether the device is connected at the first time point andthe second time point, and then it is determined whether to change theoutput power. Therefore, the specification for supplying power is notchanged, even if distortion in a recognition signal or a reception erroroccurs, until a previously connected device is disconnected from anadapter and then another device having different specification isconnected to the adapter. Additionally, damage to the device due toexcessive power supplied thereto can be prevented.

If the adapter is connected to the device at the first time point and isdisconnected from the device at the second time point, the adapter maydetect a device recognition signal (S40). The device recognition signalrefers to the signal to request a voltage change, which is describedabove.

According to an exemplary embodiment of the present disclosure, theadapter may change the specification for supplying power based on thedevice recognition signal (S50 and S60).

According to the method for controlling a power supply system, errors insupplying power caused by erroneously recognizing signals can bereduced. Further, according to the method for controlling a power supplysystem, operational stability of a general-purpose power supply devicecan be improved.

In addition, the method for controlling a power supply system accordingto the exemplary embodiment does not require any additional cable andthus can save cost.

As set forth above, according to exemplary embodiments of the presentdisclosure, a general-purpose power supply system that can be used for avariety of devices having different voltage and current levels ofdriving power can be provided.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the spirit and scope ofthe present disclosure as defined by the appended claims.

1. A power supply device to be connected to a power receiving device,the power supply device comprising: a power supply means for changing aninput power into an output voltage having a predetermined specification;a voltage port for supplying the output voltage to the power receivingdevice; a ground port for matching a ground potential of the powerreceiving device with the power supply device; a voltage change requestport for receiving, from the power receiving device, a voltage changerequest signal to change the output voltage, the voltage change requestport being provided separately from the voltage port; a control meansfor controlling the power supply means based on the voltage changerequest signal so as to change the specification which is different fromthe predetermined specification; and an adapter information output meansfor providing an adapter information indicating a type of the powersupply device to the power receiving device through the voltage changerequest port when the power receiving device is connected, wherein, thevoltage port, the ground port, and the voltage change request port areuniversal serial bus (USB) ports configured to be connected to a USBconnector.
 2. The power supply device of claim 1, wherein the type ofthe power supply device indicates that the power supply device is anoutput-voltage variable adapter.
 3. The power supply device of claim 1,the control means comprising: a control unit configured to generate acontrol signal based on the voltage change request signal input throughthe voltage change request port; and an output unit configured toprovide a feed-back to the power supply unit for changing the outputvoltage which is a different specification from the predeterminedspecification according to the control signal.
 4. The power supplydevice of claim 1, wherein the power supply device further includes adevice information recognition means for detecting a request, from thepower receiving device, for changing the specification and for detectinga voltage level of the voltage change request port.
 5. A power receivingdevice, which is configured to be disconnected from a power supplydevice, the power receiving device comprising: a voltage port forreceiving an output voltage having a specific specification from thepower supply device; a ground port for matching a ground potential ofthe power receiving device with the power supply device; a voltagechange request port for transmitting a voltage change request signal tothe power supply device and for receiving an adapter information signalfrom the power supply device; a control means for generating the voltagechange request signal for requesting a change of the specificationdifferent from a predetermined specification; and an adapter connectionswitch configured to selectively connect the voltage change request portto the control means based on a connection detection; wherein thevoltage port, the ground port, and the voltage change request port areuniversal serial bus (USB) ports to be connected to a USB connector; andwherein the voltage change request port being provided separately fromthe voltage port.
 6. The power receiving device of claim 5, wherein theadapter information signal represents capability of the power supplydevice.
 7. The power receiving device of claim 5, wherein the adapterinformation signal indicates that the power supply device is anoutput-voltage variable adapter.
 8. (canceled)
 9. The power receivingdevice of claim 6, wherein the adapter connection switch is configuredto se perform two-way communication between the power receiving deviceand the power supply device.
 10. The power receiving device of claim 5,wherein the control means comprises: a control unit configured togenerate a control signal for requesting a change of the specification;and a voltage-change-requesting unit configured to output the voltagechange request signal to the power supply device through the voltagechange request port, based on the control signal.
 11. The powerreceiving device of claim 17, further comprising: a battery; and a passswitch configured to selectively transmit the output voltage to thebattery, wherein the control means is configured to turn on the passswitch in such a manner that the output voltage is transmitted to thebattery when the output voltage, detected by the voltage detection unit,is the same as the rated voltage of the receiving device.
 12. The powerreceiving device of claim 17, wherein the voltage detection unitcomprises voltage-dividing resistors having a first register and asecond register, wherein the first register is coupled between thevoltage port and the control means, and the second register is coupledbetween the control means and the ground port.
 13. A control method of apower supply device for supplying an output voltage having a specificpower specification to a power receiving device through a USB port, thecontrol method comprising: detecting a connection of the power receivingdevice; providing an adapter information signal to the power receivingdevice when the power receiving device detected; receiving a deviceinformation recognition signal from the power receiving device when thepower receiving device detected; determining a new power specificationbased on the device information recognition signal; and supplying a newpower based on the new power specification; wherein, the adapterinformation signal indicates that the power supply device having acapability of supplying variable-output voltage to the power receivingdevice; and wherein, the device information recognition signal includesa voltage change request signal for requesting a change of the outputpower specification which is different from a predetermined powerspecification of the power supply device.
 14. The control method ofclaim 13, the USB port include a voltage change request port, andwherein the steps for providing the adapter information signal andreceiving the device information recognition signal are performed by thevoltage change request port.
 15. The control method of claim 13, whereinthe determining the power specification includes: maintaining the powerspecification, if the power receiving device is connected to the powersupply device at the first time and at the second time.
 16. The controlmethod of claim 13, wherein the determining the power specificationincludes: changing the power specification based on the deviceinformation recognition signal, if the power receiving device isconnected to the power supply device at the first time and disconnectedat the second time.
 17. The power receiving device of claim 6, furthercomprising a voltage detection means for detecting the output voltagesupplied through the voltage port.
 18. The power receiving device ofclaim 6, wherein the control means generates the voltage change requestsignal reflecting the adapter information signal.
 19. The power supplydevice of claim 1, wherein adapter information output means includes aregister and a switch connected to each other in series, and wherein theswitch selectively connects the register to the voltage change requestport.